Oral bacterial biofilms are major contributors to tooth decay (dental caries) and are a potential conduit for infection and disease. These biofilms have been shown to contain hundreds of species of bacteria and are resistant to removal and eradication by traditional oral hygiene practices, such as frequent tooth brushing or oral rinsing with mouthwash. Novel prophylactic and in situ treatment methods are therefore needed to address this problem. The central hypothesis of this effort is that small molecule effectors can reduce or eradicate oral biofilm-formation through inhibition of bacterial signaling and related metabolic pathways. Preliminary studies in my laboratory have shown that natural product-inspired organic compounds have efficacy in reducing biofilm formation by model biofilm forming bacteria. These compounds do not affect bacterial growth and propagation, but directly inhibit biofilm formation, as demonstrated by planktonic growth assays and microplate-based biofilm assays. We hypothesize that these compounds directly affect cell signaling pathways that are involved in biofilm formation. For instance, quorum sensing autoinducers, such as autoinducer-2 (AI-2) have been shown to affect cellular behavior and biofilm formation for a broad range of distantly related bacteria. Using a biomimetic approach, a library of structurally-related, organic compounds will be synthesized and screened for reduction or inhibition of biofilm formation by oral biofilm-forming bacteria. We will focus on AI-2 as the core structure for construction of our library, since derivatives of this structure could have antagonistic activity on quorum sensing pathways which have been implicated in biofilm formation. This initial study will focus on three ecologically relevant organisms: Streptococcus mutans, Streptococcus sanguinis and Actinomyces naeslundii. S. mutans has been implicated in oral disease and caries formation, while S. sanguinis and A. naeslundii are oral pioneer-colonizing commensal organisms that are involved in initial establishment of oral biofilms. Furthermore, S. sanguinis and A. naeslundii are associated with significant human diseases including endocarditis and actinomycosis. Therefore, inhibition of biofilm formation by these organisms could prevent later colonization by pathogenic organisms, such as S. mutans or Porphyromonas gingivalis that lead to tooth decay and oral disease. Inhibition of biofilm formation by all of these organisms would therefore directly affect both oral and systemic health. Our approach is highly innovative because it focuses on direct antagonism of quorum sensing and biofilm formation pathways with structural derivatives of autoinducer compounds. Rather than screening large libraries of unrelated compounds, we believe that a focused design and synthesis approach will be more effective and will enable rational improvement of compound efficacy. This collaborative research effort will be led by Prof. Nathaniel Cady, and leverages collaborations with a bioorganic/synthetic chemist (Prof. Rabi Musah - University at Albany) and an expert in biofilms/bacterial signaling, Prof. Alexander Rickard (Binghamton University). We expect several significant outcomes from this work. We will identify small molecular inhibitors of oral bacterial biofilm formation and will evaluate their effectiveness in environmentally relevant model flow-based systems. We will also investigate the effects of these compounds on intercellular signaling, which will serve as a foundation for a future R21 or R01 proposal to elucidate their mechanism of action and systematic improvement of their activity through rational design/synthesis. PUBLIC HEALTH RELEVANCE: The central hypothesis of this effort is that small molecule effectors can inhibit oral biofilm-formation through antagonism of bacterial signaling and metabolic pathways. Using a biomimetic, natural products-inspired approach, a library of structurally-related, organic compounds will be synthesized and screened for effectiveness in reducing or inhibiting biofilm formation by common orally-associated bacteria. Compounds having a strong inhibitory effect on biofilm formation will then be tested in supplemented saliva-fed flow cells to mimic environmental conditions in the oral cavity. Finally, we will explore our hypothesis that these compounds function through modulation of cell signaling behavior. The results of these studies will serve as the basis for a R21 or R01 application to elucidate their mechanism of action and develop them for therapeutic or prophylactic use.